This work presents the synthesis, volatility study and electrospray tandem mass spectrometry with variable collision induced of the isolated [(cation)2(anion)]+ of a novel series of 2-alkyl-1-ethyl pyridinium based ionic liquids, [2CN-21C2Py][NTf2]. Compared to the imidazolium based ionic liquids, the new ionic liquid series presents a higher thermal stability and lower volatility. The [(cation)2(anion)]+ collision induced dissociation energies of both [2CN-21C2Py][NTf2] and [CNPy][NTf2] pyridinium series, show an identical trend with a pronounced decrease of the relative cation-anion interaction energy towards an almost constant value for N=6. It was found that the lower volatility of the [2CN-21C2Py][NTf2] with shorter alkyl chain length, is due to their higher enthalpies of vaporization. Starting from [2C31C2Py][NTf2], the lower volatility is ruled by the combination of slightly lower entropies and higher enthalpies of vaporization, being an indication of a higher structural disorder of the pyridinium based ionic liquids than the imidazolium based ionic liquids. Dissociation energies and volatility trends supports the cohesive energy interpretation model based in the overlapping the electrostatic and van der Waals functional interaction potentials.